Transient expression of the β-glucuronidase gene introduced into barley coleoptile cells by microinjection.

A β-glucuronidase gene was introduced directly into barley (Hordeum vulgare L. cv. Kobinkatagi) coleoptile cells by microinjection and transient expression of the gene was examined. Inner epidermis tissue of coleoptiles was excised and injected with plasmid DNA, pBI221, carrying cauliflower mosaic virus 35S promoter, β-glucuronidase gene, and a nopaline synthase polyadenylation region. Histochemical assay for β-glucuronidase production showed positive enzyme activity only in coleoptile cells injected with plasmid DNA. Expression of the β-glucuronidase gene was examined chronologically using honogenates of injected coleoptile tissues. Glucuronidase activity first appeared after 6 hr, reached the maximum level 24 hr after injection, and decreased afterwards. These results suggest that microinjection of coleoptile tissues may be a useful approach for the genetic engineering of Gramineae plants in which protoplast regeneration is difficult.